It is sometimes desirable to have an optical system with multiple fields of view. For example, Grech U.S. Pat. No. 4,155,626 discloses spectacles which provide a wide angle field of view in a peripheral region and an essentially normal field of view without magnification or demagnification in a central region. Spectacles of this type are of particular advantage for individuals with tunnel vision in that the field of view can be enlarged beyond the "tunnel" which defines the normal field of view.
According to the Grech patent, a wide angle lens system is mounted on a spectacle frame and the wide angle lens system includes a central region with flat, parallel surfaces which provide unit magnification. The concept of the Grech patent is sound. However, if the flat surfaces are not aligned quite accurately with the line of sight, the observer may see several circular segments and the information received may be somewhat distorted.